1. Field of the Invention
The present invention relates to watering systems and, more particularly, relates to animal watering systems for supplying drinking water to lab animals or the like and to watering valves usable with such systems.
2. Discussion of the Related Art
It is desirable in a variety of fields to reliably and automatically supply drinking water to laboratory animals or the like upon demand. Such water is typically supplied to animals housed in cages mounted on a rack system supplied with water by a water manifold. One such cage and rack system incorporating a watering system is disclosed in U.S. Pat. No. 5,042,429, which issued to Dietrich et al on Aug. 27, 1991. The system disclosed by Dietrich et al. houses a plurality of laboratory animals in rows of cages stacked one on top of the other on a rack. The cages are supplied by a common water manifold.
Watering systems of the type disclosed by Dietrich et al. typically must accommodate frequent removal of the individual cages from the rack, e.g. for testing of animals housed therein or for cleaning of cages. Such systems must also seek to minimize the cross-contamination of the animals housed in the various cages. Dietrich et al. attempts to accommodate these requirements by connecting the individual cages of its system to the manifold by a quick-connect coupling system designed to reduce the likelihood of cross-contamination. This coupling system includes, in the case of each cage, a watering valve fixed to the cage, a male fitting attached to the watering valve and extending rearwardly from the cage, and a female fitting extending from the water manifold. The male fitting engages the female fitting with a friction fit when the cage is properly positioned on the rack. According to the Dietrich et al. patent disclosure, the friction-fit type quick connect coupling facilitates removal and replacement of the cages, and the internal watering valve prevents or at least inhibits cross-contamination between cages.
The friction-fit type quick connect coupling employed by Dietrich et al., while facilitating removal and replacement of the cage, exhibits the disadvantage of not "locking" the cage in position so that if the cage is bumped or improperly positioned, the coupling may leak and/or fail to deliver water to the animal. The need has therefore arisen to provide an animal watering system which, while facilitating removal and replacement of cages and preventing or at least inhibiting cross-contamination between cages, also reliably delivers drinking water to the animals in the cages without leakage.
A watering valve of the type usable in the system disclosed by Dietrich et al. is disclosed in U.S. Pat. No. 5,065,700, which issued to Cross on Nov. 19, 1991. The valve disclosed by Cross employs a housing having an inlet and an outlet connected by an elongated longitudinal bore, a valve element located adjacent the inlet, and an elongated valve stem which extends through the bore, which projects out of the outlet, and which, when deflected by the animal, opens the valve element to permit the passage of water through the valve housing. A movable shield or shutter member is provided adjacent the outlet to inhibit the animal from stuffing bedding material or other debris into the outlet and unintentionally lodging the stem in its actuated position to cause the valve to stick in its open position.
The watering valve disclosed by Cross suffers from several drawbacks and disadvantages. For instance, its shutter or shield is rigid and thus must move with the stem or actuating lever to permit valve opening. This shield is thus subject to corrosion and jamming which may inhibit or even prevent valve opening or which may cause the valve to stick in its open position. Another disadvantage arises from the fact that the distal end of the stem is positioned outside of or at least near the outlet of the valve housing. As a result, an animal may unintentionally hold the valve open with its feet if it perches on top of the valve housing. Moreover, because neither the shield nor the valve element applies sufficient return forces to return the actuating lever or stem to its position of rest, a helical return spring must be provided to close the valve when the animal releases the valve. This spring unduly increases the complexity of the valve and is itself subject to corrosion and breakage which could render the valve inoperable. Finally, since the valve element employs conventional elastomeric seals and associated elements, it may be clogged if corroded or if chemicals in the water cause swelling or distortion of the elastomeric components of the valve element.